Quantum Computer Architectural Design: A Comprehensive Examination

This report provides a detailed overview of quantum computer architectural design. It begins with an introduction to quantum computing and its impact, discussing the principles of qubits and their coherence. The report delves into the quantum von Neumann architecture, particularly for trapped ions, highlighting the importance of high κ values and memory multiplexing. The discussion also includes the Quantum 4004, based on the classical Intel 4004 CPU. The report emphasizes the critical role of quantum error correction (QEC) in mitigating errors arising from decoherence and gate operations. It examines the five layers of abstraction in quantum computing and the need for long coherence times. The report also explores the challenges and potential of quantum computers, including the use of Shor's algorithm for factorization and the importance of fault tolerance. Ultimately, the report concludes that quantum computers, despite being in their early stages, are poised to revolutionize technology.

Running head: QUANTUM COMPUTER ARCHITECTURAL DESIGN
Quantum computer architectural design
Name of the Student
Name of the University
Author Note

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Abstract
Quantum Computing is making a great impact in the field of science and development in
today’s world. In this paper, a vivid description on the roles of the Quantum Computers has
been discussed. Quantum architecture is based upon the principle of the coherence of the
qubits and the computing is capable of acquiring crucial quantum information between the
quantum computers. The Quantum von Neumann architecture for trapped ions is discussed
here that uses memory multiplexing for full-scale quantum computation. The Quantum von
Neumann architecture for trapped ions in quantum computing has also been discussed in the
course of this assignment to highlight the importance of the trapped ions, as they are capable
of generating a high κ value. A description of the he Quantum 4004 has also been discussed.
It is based upon the classical Intel 4004 CPU. Conclusions from this report can be drawn as
Quantum computer will be able to shape the future of the technology despite being in its
initial stage of development.

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Table of Contents
Introduction................................................................................................................................3
Discussion..................................................................................................................................5
1. Quantum computer.............................................................................................................5
2. Quantum von Neumann architecture.................................................................................8
3. A quantum von Neumann architecture for trapped ion quantum computation................12
4. The Quantum 4004...........................................................................................................15
Summary..................................................................................................................................18
References................................................................................................................................21

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Introduction
From the early decades of the technological development, several equipment like that
of the transistors in the integrated circuits or the IC has expanded to almost a double in every
two year. There has been studies, which has discussed this type of an exponential growth, and
it aided in an exponential growth of the calculation power in the past (Beck, 2018). In the
early years of this century, the clock speeds of the integrated circuits grew exponentially also
but the problem with those clock speeds was that the clock speeds reached to the levels that
required cooling and the cooling of the clock speeds inherently limited the clock speeds
(DiVincenzo, 2000). To avoid this type of problem, there was necessity to maintain a steady
increase the in the exponential growth of the calculation power and that could only be
attained by decreasing the size of the transistors and incorporating multiple cores into the
integrated circuits (Van Meter, 2014). This decrease in the size of the transistors will make
them lead to a size of the atomic level which that is ultimate and from there, either one will
have to discover new techniques for computing the results or will have to be sufficed with the
lower increase in computation power over the time. This challenge regarding the speed of
computation is resolved with the help of Quantum Computation (Prince, 2014).
Quantum computation is the phenomenon of quantum mechanics that is attained
through the help of a series of computational techniques. Devices relying on these
computational techniques are known as the quantum computers. These computers are
different to that of the normal computers. The normal computers are not able to perform the
quantum functionalities and the algorithms, as they are composed of binary bits whereas the
quantum computers are composed of the quantum bits or qubits in simpler terms. These
qubits usually remain in the superposition of states (Yanofsky, Mannucci & Mannucci,
2008). An ideal quantum computer is generally known with the name of Quantum Turing

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Machine or (QTM). One of the major scientists in the field of quantum mechanics is Richard
Feynman. The concept of quantum computing is still at the early stages of development but
with relative efforts and technological developments, it is expected to bypass all the barriers
of computational activities in the field of quantum mechanics (Di Ventra, & Pershin, 2013).
Several valid experiments have been carried out in the past and are still being carried out to
get closer to the objectives of quantum computing. Along with the experiments several
theoretical researches are being carried on that is mostly being funded by the governments.
These quantum computers are mainly used for the specific purposes such as business, trade,
environmental and national security purposes.
On the basis of the computer architectures, about how the computer systems are to be
organized, designed and implemented are classified in the form of architectural style known
as the von Neumann architecture. This form of computer architecture has been derived from
the name of John Von Neumann who was the first person to enlist the requirements of the
electronic computer (Vlasov, 2000). His researches have a deep impact on the computer
systems of the present days. The computer systems that do not exhibit the same
characteristics as depicted by the computers architecture are known by following a non-Von
architecture.
The purpose of this assignment is to discuss the various aspects of the Quantum
computation based on the quantum architectural design. The areas related to the quantum
mechanics with the integration of the quantum mechanics has been discussed in this
assignment. A brief idea about the quantum computers have been discussed in this paper. The
von Neumann architecture has been outlined in this assignment along with the quantum von
Neumann architecture for a trapped ion quantum computation. The fourth section deals with
the idea of Quantum 4004. Ultimately, a summary of the whole assignment has also been
provided.

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Discussion
This section of the paper deals with the discussion of the quantum computers, the
quantum von-Neumann architecture, the quantum von-Neumann architecture for a trapped
ion quantum computation and the quantum 4004.
1. Quantum computer
A quantum computer can be described as a computer device that is based on the
structural configurations of the quantum mechanical system. One of the properties exhibited
by the quantum computers is the principle of superposition. They also depict their credibility
by solving relatively difficult tasks as compared to that of the classical computer devices. The
information stored in the quantum computers are in the form of two level mechanical systems
that are known by the name of quantum bits or qubits (Brandl, 2017). This qubits in relation
to the quantum mechanics are considered as the noise-induced de-coherence. Due to this
phenomenon of the qubits, the information storing capacity is limited. The Hilbert space
created by the isolation of the qubits are prone to that of the introduction of the error in the
computational activities through the quantum mechanical gate operations. The correction of
these errors should be done in order to avoid the further disputes in the quantum
computational activities (Imre & Balazs, 2013). These errors are known by the name of
Quantum Errors or QE and the techniques implemented to correct these errors are known as
the Quantum Error Correction or QEC mechanism. This mechanism is implemented in the
Quantum Computers as these helps in correcting the errors that generally creeps up due to de-
coherence and the multiple gate operations (Hirvensalo, 2013).
In computer science, the concept of the abstraction layers plays a huge part and can be
implanted in the quantum computers. The layers in quantum computing is generally of a total
of five in number. These layers are situated in the form of a stack that is one on top of the

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other (Chow et al., 2014). The bottommost layer of the layer system is comprised of the
physical layer that is responsible for all the physical gate operations. The layer situated right
above those layers is known with the name of virtual layer that supports the usage of the open
loop error cancellation (Childress & Hanson, 2013). The mechanism of the quantum error
correction is executed in the third layer. The fourth layer is named as the logical layer where
a substrate for quantum computations is structured. The fifth and the ultimate layer is known
with the name of Application layer that is known for providing an interactive interface to the
user who then gives the input. The application layer accepts the input and the quantum
computational activities are performed thereafter. Studies at the present are focusing on the
automation of the assembling and compilation of the sequence which are similar to that of the
assemblers and the compilers (Kloeffel & Loss, 2013). These researches and the studies are
taking place in the modern days to emphasize on the impact of the computing machines in the
present world. Thus it is evident that requirement of the quantum error correction is essential
in the correction of the stated errors.
An ideal quantum computer needs to follow the basic five characteristics in order to
exhibit itself successfully as a device capable of performing the quantum computations
(Humphreys et al., 2013). These attributes characterized by the quantum computers need to
contain well characterized qubits, they should have the ability to determine the state of the
qubits, they should have long de-coherence terms, they should have a universal state of the
quantum gates and should also exhibit a qubit oriented measurement capability. These five
characteristics are very much required for a computer system to be termed as the quantum
computers. Quantum electronic devices with trapped ions can be one of the possible devices
that can be termed as the quantum computers. Besides that, the devices containing quantum
dots in silicon and ultra cold atoms can also be potential quantum computers (Aaronson,
2013). It is challenging to find out a general architecture for the quantum computers such as

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the von Neumann architecture for a classical computer since the communication from one
qubit to another qubit has contrasting reflection from one technology to the other. Although
there have been several experiments regarding the advancement of the quantum
computational activities the area of quantum mechanics is still at the initial stage. For this,
several new researches and development of the existing modules are taking place worldwide.
The errors in the computational process of quantum computing arise from many
sources. From all these sources, there are two sources that can be highlighted as the main
sources of errors (Aasen et al., 2016). The first type of the error is known as the storage error
and this error mainly caused due to the noise produced from environment coupling in the
computers. The second type of the error is known as the de-coherence error and this error
mainly caused due to the unbalanced gate operations in the quantum field. The role of the
QEC is to correct these errors to produce a more accurate and effective result. The errors in
long Quantum Computations must be much below of the fault tolerant limit (Menicucci,
2014). This is essential for the QEC to be effective otherwise, the application of the QEC
would be meaningless if the level surpasses the fault tolerant limit. From this it is evident that
the errors in the during the quantum computational activities must be lowered to a significant
level in order to get greatly benefitted from the Quantum Error Correction mechanism
(Barends et al., 2014). For series of computation activities with just on processing zone the
coherence time of the qubits is required to be in proportion with that of the number of the
qubits in the quantum computer in order to maintain a constant error of the memory. That is,
the coherence time should increase with the increasing number of the qubits in the quantum
computation process in the quantum computers.
The difference in the computation speeds of varying architectural modules is heavily
dependent upon the complex algorithmic structures that are executed during the
computational process. Generally, Shors’s algorithm is used as ideal point of computational

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speed because it helps to allow the fast factorization of the large numbers (Saffman, 2016). A
number with Shor’s algorithm can be factorized if the number is of order N and has a binary
bit length of order n. Different architectural models can be implemented for the execution of
the Shor’s algorithm and these models can be easily connected to their execution time. To
achieve this process, it is very much required for a logical clock speed of the hardware that
states the number of operations can be implemented on the logical qubits at a particular rate
and this will indicate that quantum error correction is being executed in the logical operations
of the logical qubits (Raychev, 2015). One of the architectural model that is widely used in
the computational process of error correction mechanism is the Beckman Chari Devabhaktuni
Preskill or the BCDP model. This model requires the interaction between the just next
neighbors only. The model is known for using (5n+3) qubits to factorize a number that has a
binary bit length of order n and the time scales for the execution process is almost as ∼ 54n3 .
Another of such architectural model is the Neighbor only Two qubit gate Concurrent
architectural model or the NTC model. It is executed with the next neighbors only
interactions in a 2n2 qubit space and has a time scale as ∼ 20n2log2(n).
2. Quantum von Neumann architecture
In the context of the computer architectures about how the computer systems are
designed, structured and organized the role play of the von Neumann architecture is presented
as a reference of comparison. This is evident in most of the cases since almost every virtually
rooted computer is based on the structural plan of this architecture (Rédei, & Stöltzner,
2013). The name of this strong architectural model is derived from the name of John von
Neumann, who was the author of two important papers published in the year of 1945. These
two papers are contributed as Goldstine and von Neumann 1963 and von Neumann 1981.
Von Neumann was also a coauthor of a third paper in the year of 1946. He was the first
person to present with the requirements of a general purpose electronic computer. The idea of

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his papers stated the rigid effect on the development of such electronic machines (Lloyd,
2013).
In 1952, the construction of the EDVAC was possible due to the design of von
Neumann. Although the first computer of this genre was first constructed and operated at The
University of Manchester in Manchester, England and was named as Mark I. It had a 96 word
memory and a executed its first program in the year 1948. The time taken for the execution of
the instructions was 1.2 milliseconds that was an astonishing figure according to that period
of time (Van Meter & Horsman, 2013). In today’s world the execution time of the program
would have been 0.00083 millions of instructions per second using the MIPS terminology. In
contrast to the past, someof the supercomputers in the modern days is considered to run with
an excess speed of 1000 MIPS. However, these super computers as considered to be
following and based on the von Neumann architectural model to a large amount.
Many computers for several years have considered as the non-von Neumann
computers due to their configuration state or considered as to be following the minimum of
the von-Neumann architecture. It is being tried and efforts are being put for over the years to
break free from the old concept of following the traditional von Neumann architecture with a
purpose of being more productive and more usable as computers (Holmes, Kadin & Johnson,
2015). The requirements of the fifth generation of the computers demanded an evolution of
the architectural models and in addition to that, it also demanded that the hardware and the
software were set free from the bound of the von Neumann architectural model. However, it
is true that von Neumann architectural model plays an integral role in setting up of the basic
structures of the computer systems as it is the way it should work (Yamaoka et al., 2016). To
find out the present scopes for the computer designers and developers in contrast to the future
scope of the computer designers and the developers, emphasis on the on the critical

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understanding of the von Neumann architecture is required rather than just highlighting the
implications of the same architectural model (Chougule, Sen & Dongale, 2017)).
At first von Neumann, started discussing about the wide concept of the general
purpose computing machines. According to him, these computers consisted of mainly four
organs. These four organs came with the connection to the human operator. These four
organs are classified as arithmetic, memory, control and connection. In simpler words, it can
be said that a computing model consisted of an arithmetic unit, a logical unit, a memory and a
combination of the input and the output devices (Theis & Wong, 2017). According to von
Neumann the main objective of the computing systems were just not only to store data and
represent the results of the computation but also to store the data or the instructions that are
required for the computational activities. The computational procedure of the hardware was
considered to be connected to a hardware for the special purpose machines. For a general
purpose, one of the instruction is to be modifies in which they are being acted upon
(Kvatinsky et al., 2014). Therefore, it was necessary to encode the instructions into a form of
the numbers and store the data and the numbers simultaneously in the same memory. This
whole scenario is considered as a reference to the contribution of the von Neumann
architecture model for ideal computing machines. Later von Neumann defined the control
organ as the source, which would be able to store the coded instructions in the memory.
According to him, if the machine was able to differentiate between the number from its order
then the orders and data were able to reside in the same set of memory (Bochmann et al.,
2013). However, there is no dissimilarity between the number and order in memories. The
control counter, also known as the program counter is considered to be the carrier of the next
instruction and also of the word which is fetched to be executed. This happens according to
the control unit that is the process takes place according to what is treated as the data or an
order by the control unit.

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One of the disadvantages of the above mentioned process is that the instructions can
overwrite other instructions creating a self modified program. This overwriting of the
instructions were considered as one of the disadvantage for several years because the
requirement of debugging of the programs and the introduction of the new program snippets
in some parts of the program for some particular circumstances. Possibilities are there that the
developments and innovations in these fields will open a gateway for the possibilities
depicted by the above mentioned characteristic (Traversa et al., 2014). The main devotion of
von Neumann was in the field of the of designing the arithmetic unit which he declared as
one of the four organs of the general purpose computing machines. The further information
of this was not important according to the view of his organization and the future prospect
governing the developments in the fields of computing machines and devices. The main
abilities of the arithmewtic unit was bounded to the performance of some of the random
groups of the possible arithmetic operations. According to von Neumann, the inner economy
of the arithmetic unit is overseen by the sacrifice between the wish of the speed of the
operations and the desire for the non complexity and the cheapness of the machines (Lin et
al., 2015). It is interesting to know that this issue carried on for several more years and
dominated the design decisions. In modern days, it has been framed almost as a myth that the
cost of the hardware is not to be accounted as it is not so important.
The concepts put forward with the help of the von Neumann architecture were so
much significant that they proved to be the major source of foundation for the development
of the early computing machines and also for the systems that form a substantial part of the
modern days. Accordingly, from the above discussions of the above sub sections of this main
section it can be concluded that the von Neumann architectural model formed the basic
structural model of the modern day computing machines (Konar et al., 2016). The